Including Hong Kong and Macau would bring China to 45% of the US GDP in 2011.

2000-2004 China increased 34% from 12.3% to 16.4% against the USA and the 2004 economy was 60% larger than 2000. The US GDP increased 19.6% over the same time.

2004-2008 China almost doubled from 16.4% to 32% against the USA and the 2008 economy is more than double than the 2004 economy in US dollars. 2008 China is almost double in yuan terms the 2004 China. The US economy increased 22.4% over the same time. The currency has moved about 22.5% [currently 21%, expect some more movement by the end of 2008].

Repeating the 2000-2004 time frame with 34% moves would place China passing the US economy in the 2025-2028 period. However, this would mean the US currency would stabilize at current exchange rates.

Repeating the 2004-2008 time frame with doubling moves would place China passing the USA in 2015-2017. The exchange rate would be 4.1 yuan to one US dollar.

China could start to grow slower than it did from 2000-2004. The United States seems unlikely to grow faster from 2011-2015 than it did from 2000-2004. China's currency seems likely to continue to strengthen.

Economywatch has a projections from 2010 to 2015 based on OECD, IMF, UN, World Bank and CIA data. Economywatch is actually projecting a slightly higher level for China's GDP in local currency. They are expecting a few fractions of a percent higher annual GDP growth. If they are correct then it is a question of what the RMB and USD exchange rate will be to calculate a nominal GDP value for China. I do not see how China's currency would appreciate less than 15% versus the US Dollar over 5 years and should be at least 30%. I am projecting a 44% increase in the value of the RMB relative to the USD. It would be a 71% appreciation if the exchange rate matched the implied exchange rate projected for 2015.